Potentiae receptivae sunt essentia respectu actus essendi et materia respectu formae. Suarez autem essentiam cum existentia identificat. Secundum Suarezium essentia in potentia est merum nihil, ideoque munus potentiae receptivae respectu to? esse exercere nequit. Actualitas essentiae in actu est eius esse; actualis essentia ergo non exigit ullum aliud esse, a se distinctum. Quamquam essetia realiter ab esse non distinguitur, sine eo tamen concipi potest. Essentia qua quidditas cum conceptu et definitione artissime conectitur. Quapropter doctrina Suarezii occasionem critice quaerendi praebet: Si quidditas et esse idem sint, nonne etiam in conceptu adaequato quidditatis identitas ista manifestari debeat? Hac identitate autem supposita, num essentia sine esse concepta eadem remaneat? Amplius, si esse cum essentia identificetur, num subiectum aliquod remaneat, de quo esse sine nugatione praedicare poterit? Quid sit potentia receptiva to? esse? Arriaga sententionem Suarezii de essentia et esse observat, in doctrina autem de materia prima immo ultra procedit. Dum Suarez materiae primae actualitatem propriam assignat, Arriaga non haesitat, rationem substantiae ei imputare. Nostro iudicio tamen doctrina Suareziana de potentiis receptivis contra mechanicismum vel sententiam illam a G. Frege traditam, quae esse ad notionem trivialem reducit, parum valet; ad resistendum his doctrinis in metaphysica multo magis doctrina Thomistica iuvabit, quae relationem participationis inter potentiam et actum ponit.

Receptive potencies are the essence in relation to the act of being (esse) and the matter in relation to the form. Suárez identifies the essence with the existence. A potential essence, according to Suarez, is nothing; therefore it cannot be receptive potency for being (esse). The actuality of an actual essence is its being (esse). Hence, the actual essence does not need to receive any further being distinct from it. Essence does not differ really from being (esse); nevertheless, we can conceive it without being. Essence as "whatness", quiddity, is closely connected with concept and definition. In this regard we may make some critical remarks on Suarez's doctrine: If the "whatness" is identical to the being (esse), this fact has to be reflected in the adequate notion of the "whatness". If it is so, it seems that the essence conceived without being (esse) is not the same essence any more. Furthermore: If essence and existence are identified, what is it to which existence can be non-trivially ascribed? What is the receptive potency for being (esse)? Arriaga follows Suárez in the doctrine of essence and being, in his teaching on the prime matter however he goes even further. Whereas Suárez ascribes to the prime matter its own actuality, Arriaga assigns to it some attributes of substance. In contradistinction to the Suarezian conception of receptive potencies, the Thomistic doctrine of the relation of participation between potency and act permits metaphysics to withstand the threats of mechanicism and the post-fregean trivialization of the notion of being (esse).